US5772978A - Process for producing tungsten oxide - Google Patents
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- US5772978A US5772978A US08/639,020 US63902096A US5772978A US 5772978 A US5772978 A US 5772978A US 63902096 A US63902096 A US 63902096A US 5772978 A US5772978 A US 5772978A
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- polytungstate
- stable oxide
- peroxide
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- 238000000034 method Methods 0.000 title claims abstract description 55
- QGLKJKCYBOYXKC-UHFFFAOYSA-N nonaoxidotritungsten Chemical compound O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1 QGLKJKCYBOYXKC-UHFFFAOYSA-N 0.000 title claims abstract description 43
- 229910001930 tungsten oxide Inorganic materials 0.000 title claims abstract description 43
- 230000008569 process Effects 0.000 title claims abstract description 41
- 239000002243 precursor Substances 0.000 claims abstract description 11
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 31
- 150000002978 peroxides Chemical class 0.000 claims description 29
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 20
- 239000000843 powder Substances 0.000 claims description 17
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 claims description 15
- 230000001476 alcoholic effect Effects 0.000 claims description 12
- 238000001035 drying Methods 0.000 claims description 11
- 229910052721 tungsten Inorganic materials 0.000 claims description 11
- 239000010937 tungsten Substances 0.000 claims description 11
- 238000006243 chemical reaction Methods 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 claims description 10
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 10
- 239000002904 solvent Substances 0.000 claims description 8
- 239000002253 acid Substances 0.000 claims description 7
- 238000009835 boiling Methods 0.000 claims description 5
- 230000001131 transforming effect Effects 0.000 claims description 2
- 239000000243 solution Substances 0.000 description 103
- 238000000576 coating method Methods 0.000 description 13
- 238000010992 reflux Methods 0.000 description 10
- 239000011248 coating agent Substances 0.000 description 8
- 239000000203 mixture Substances 0.000 description 8
- 230000005540 biological transmission Effects 0.000 description 6
- 238000009830 intercalation Methods 0.000 description 6
- -1 peroxy tungstic acid Chemical compound 0.000 description 6
- 239000007787 solid Substances 0.000 description 6
- 239000000758 substrate Substances 0.000 description 6
- 239000008367 deionised water Substances 0.000 description 5
- 239000011521 glass Substances 0.000 description 5
- 230000020477 pH reduction Effects 0.000 description 5
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 description 4
- 239000000654 additive Substances 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- WEVYAHXRMPXWCK-UHFFFAOYSA-N Acetonitrile Chemical compound CC#N WEVYAHXRMPXWCK-UHFFFAOYSA-N 0.000 description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 3
- 229910004801 Na2 WO4 Inorganic materials 0.000 description 3
- 230000002378 acidificating effect Effects 0.000 description 3
- 238000005341 cation exchange Methods 0.000 description 3
- 238000005342 ion exchange Methods 0.000 description 3
- 239000003456 ion exchange resin Substances 0.000 description 3
- 229920003303 ion-exchange polymer Polymers 0.000 description 3
- 229910001416 lithium ion Inorganic materials 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 230000003287 optical effect Effects 0.000 description 3
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- PBYZMCDFOULPGH-UHFFFAOYSA-N tungstate Chemical class [O-][W]([O-])(=O)=O PBYZMCDFOULPGH-UHFFFAOYSA-N 0.000 description 3
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- 238000001237 Raman spectrum Methods 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- YRKCREAYFQTBPV-UHFFFAOYSA-N acetylacetone Chemical compound CC(=O)CC(C)=O YRKCREAYFQTBPV-UHFFFAOYSA-N 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 239000007844 bleaching agent Substances 0.000 description 2
- 229920001429 chelating resin Polymers 0.000 description 2
- 238000000151 deposition Methods 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 239000000499 gel Substances 0.000 description 2
- 238000001879 gelation Methods 0.000 description 2
- 238000010348 incorporation Methods 0.000 description 2
- 230000002687 intercalation Effects 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 125000000864 peroxy group Chemical group O(O*)* 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- 229910006065 SO3 Li Inorganic materials 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 150000004703 alkoxides Chemical class 0.000 description 1
- 239000003125 aqueous solvent Substances 0.000 description 1
- 238000004061 bleaching Methods 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000003729 cation exchange resin Substances 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000000084 colloidal system Substances 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 229910021419 crystalline silicon Inorganic materials 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000000502 dialysis Methods 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000000840 electrochemical analysis Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 150000002367 halogens Chemical class 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000003495 polar organic solvent Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- XMVONEAAOPAGAO-UHFFFAOYSA-N sodium tungstate Chemical compound [Na+].[Na+].[O-][W]([O-])(=O)=O XMVONEAAOPAGAO-UHFFFAOYSA-N 0.000 description 1
- 238000001694 spray drying Methods 0.000 description 1
- 238000003892 spreading Methods 0.000 description 1
- 230000007480 spreading Effects 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000012085 test solution Substances 0.000 description 1
- UONOETXJSWQNOL-UHFFFAOYSA-N tungsten carbide Chemical compound [W+]#[C-] UONOETXJSWQNOL-UHFFFAOYSA-N 0.000 description 1
- ZNOKGRXACCSDPY-UHFFFAOYSA-N tungsten trioxide Chemical compound O=[W](=O)=O ZNOKGRXACCSDPY-UHFFFAOYSA-N 0.000 description 1
- 238000001771 vacuum deposition Methods 0.000 description 1
- 230000004584 weight gain Effects 0.000 description 1
- 235000019786 weight gain Nutrition 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G41/00—Compounds of tungsten
- C01G41/02—Oxides; Hydroxides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G41/00—Compounds of tungsten
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/02—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition
- C23C18/12—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition characterised by the deposition of inorganic material other than metallic material
- C23C18/1204—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition characterised by the deposition of inorganic material other than metallic material inorganic material, e.g. non-oxide and non-metallic such as sulfides, nitrides based compounds
- C23C18/1208—Oxides, e.g. ceramics
- C23C18/1216—Metal oxides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/02—Amorphous compounds
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
- C01P2002/84—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by UV- or VIS- data
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
- C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
- C01P2004/84—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases one phase coated with the other
- C01P2004/86—Thin layer coatings, i.e. the coating thickness being less than 0.1 time the particle radius
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/10—Solid density
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/60—Optical properties, e.g. expressed in CIELAB-values
Definitions
- This invention relates to producing tungsten oxide.
- Tungsten oxide (WO 3 ) is an electrochromic material which has been widely used as the basis for electrochromic-based devices such as displays and light modulating windows. Numerous methods are known for depositing tungsten oxide coatings onto a substrate. Vacuum deposition methods such as sputtering and evaporation are the most commonly used processes, although solution deposition methods are known as well. These solution-based methods generally involve one of three general types of tungsten oxide precursors: colloidal sols, alkoxide derivatives, and peroxy tungstic acid.
- the invention features a process for producing a tungsten oxide precursor solution in which a peroxypolytungstate solution is converted to a stable oxide polytungstate solution.
- the process includes the step of treating a polytungstate solution (e.g., an acidified ammonium metatungstate solution) with a peroxide (e.g., hydrogen peroxide) to form the peroxypolytungstate solution.
- a polytungstate solution e.g., an acidified ammonium metatungstate solution
- a peroxide e.g., hydrogen peroxide
- the amount of peroxide preferably ranges from about 0.2 to about 2.0 moles of hydrogen peroxide per mole of tungsten, more preferably from about 0.7 to about 1.3 moles of hydrogen peroxide per mole of tungsten.
- the process preferably includes the steps of (i) drying the peroxypolytungstate solution to form a powder; (ii) dissolving or dispersing the powder in a solvent that includes an alcohol (e.g., ethanol) to form an alcoholic solution; and (iii) heating the alcoholic solution (e.g., at its boiling point) to convert the peroxypolytungstate solution to the stable oxide polytungstate solution.
- a solvent that includes an alcohol (e.g., ethanol) to form an alcoholic solution
- heating the alcoholic solution e.g., at its boiling point
- the stable oxide polytungstate solution preferably is substantially free of peroxide species (e.g., tungstate ions, clusters, polymers, and/or colloids containing peroxide chemical bonds) and peroxytungstic acid. Moreover, the stable oxide polytungstate solution preferably includes no greater than about 50% by weight water, more preferably no greater than 20% by weight water, and even more preferably no greater than about 8% by weight water. Even more preferred are stable oxide polytungstate solutions that are substantially free of water.
- the invention also features a process for producing tungsten oxide by transforming the above-described stable oxide polytungstate solution to tungsten oxide.
- the transformation is preferably effected by drying the stable oxide polytungstate solution to form a residue, and then heating the residue at a temperature ranging from about 100° C. to about 350° C., and more preferably from about 150° C. to about 250° C.
- the invention features a process for producing a tungsten oxide precursor solution that includes converting an acidified ammonium metatungstate solution to a stable oxide polytungstate solution, e.g., by exposing the acidified ammonium metatungstate solution to a peroxide to form a peroxypolytungstate solution, and then converting the peroxypolytungstate solution to the stable oxide polytungstate solution.
- the stable oxide polytungstate solution can then be transformed to tungsten oxide.
- Tungsten oxide precursor solution refers to a sol or solution that can be transformed to tungsten oxide.
- Polytungstate solution refers to an essentially clear or slightly translucent sol or solution that includes tungstate ions, polymers, and/or colloidal particles.
- Peroxypolytungstate solution refers to an essentially clear or slightly translucent sol or solution that includes tungstate ions, polymers, and/or colloidal particles, and is further characterized by the presence of peroxy chemical bonds as manifested, e.g., in a tungsten-peroxy peak appearing at about 550-570 cm -1 in a Raman spectrum of the corresponding dried solid.
- Acidified ammonium metatungstate solution refers to a polytungstate solution prepared by acidifying an ammonium metatungstate solution that includes species having the nominal formula (NH 4 ) 6 H 2 W 12 O 40 +XH 2 O.
- “Stable oxide polytungstate solution” refers to a solution or sol formed from a peroxypolytungstate species in which at least a substantial number of the peroxide bonds have been converted to oxide bonds. The conversion is manifested, e.g., as a decrease in the tungsten-peroxy peak appearing at about 550-570cm -1 in a Raman spectrum of the dried solid corresponding to the initial peroxypolytungstate and the appearance of a broad peak at 700-800 cm -1 (corresponding to the dried solid form of the oxide polytungstate). Typically, a reduction of at least about 50% in the area of the tungsten-peroxy peak is desirable.
- the conversion is generally accompanied by changes in the polytungstate species, e.g., growth of the species. It is believed that these changes enable subsequent transformation of the oxide polytungstate to a tungsten oxide composition particularly suitable for electrochromic devices.
- tungsten oxide compositions prepared according to the invention generally are reversible with respect to lithium intercalation when fired at 150° C.-250° C.
- the compositions return substantially to their original uncolored state.
- the oxide polytungstate solution is "stable" in the sense that it exhibits negligible changes in viscosity, appearance, and properties over time scales typically encountered for storing solutions for subsequent coating (e.g., on the order of several days to several months) under typical storage conditions.
- the invention provides a reliable, reproducible method for producing electrochromic tungsten oxide.
- the method uses inexpensive and readily available starting materials, and can be performed in a few hours.
- the method does not produce corrosive by-products and results in stable, ion-intercalating tungsten oxide materials suitable for use in electrochromic devices.
- the invention features a process in which a tungsten oxide precursor solution is transformed to tungsten oxide (e.g., in the form of a coating on a substrate such as glass or plastic).
- the precursor solution is preferably prepared by treating an initial polytungstate solution with a peroxide to form a peroxypolytungstate solution, followed by converting the peroxypolytungstate solution to a stable oxide polytungstate solution.
- the initial polytungstate solution is preferably in the form of an aqueous solution, and may be prepared according to a variety of methods, including acidification of soluble tungstate salts (e.g., Na 2 WO 4 ) or hydrolysis of tungsten alkoxides.
- a particularly preferred initial polytungstate solution is an aqueous solution of acidified ammonium metatungstate ("AMT").
- AMT solutions are clear, colorless, and resist forming coagulated gels. They may be prepared at ambient temperature by eluting an aqueous ammonium metatungstate solution (containing, e.g., about 20 g of ammonium metatungstate per 100 g of distilled, de-ionized water) through an acidified cation exchange column or by mixing the metatungstate solution with the acidified cation exchange resin, followed by removing the resin by filtering, decanting, or a comparable method.
- Other acidification methods e.g., dropwise addition of an acid such as HCI, followed by dialysis may be used as well.
- the cation exchange column offers the advantage of removing unwanted cations without the need for further purification.
- suitable acidified cation exchange media are commercially available and include Amberlite IR 120+ acidic ion exchange resin from Aldrich Chemical Co. of Milwaukee, Wis.
- the acidification reaction is preferably conducted such that the product solution has a pH no greater than about 2.0.
- the initial polytungstate solution is preferably stable over the time scale generally encountered in preparing the tungsten oxide precursor solution (e.g., on the order of several hours to several days) in the sense that it exhibits negligible changes in viscosity, appearance, and properties over this time period.
- the initial polytungstate solution also preferably has the ability to be dried to a powder and then dissolved in aqueous or polar organic solvents (e.g., alcohols) to form an optically clear, substantially gel-free solution.
- the next step is to treat the initial polytungstate solution with a peroxide to form a peroxypolytungstate solution.
- a peroxide solution is added to the polytungstate solution with stirring for a period of about 20 minutes.
- the preferred peroxide is hydrogen peroxide.
- the amount of peroxide is selected to form a peroxypolytungstate which can be dried without substantial gelation, easily re-dispersed or re-dissolved following drying, and readily converted in solution to a stable oxide polytungstate solution.
- the amount of peroxide typically ranges from about 0.2 to about 2 moles of hydrogen peroxide per mole of tungsten, and more preferably from about 0.7 to about 1.3 moles.
- the initial polytungstate solution is not AMT, but rather the product of, e.g., acidification of an alkali tungstate such as Na 2 WO 4 , particular care must be taken prior to and during the peroxide treatment to avoid formation of intractable gels or coagulated solids. This may be accomplished, e.g., by using a dilute tungstate salt solution and collecting the acidified product directly into the peroxide solution. In addition, the amount of peroxide may have to be adjusted to ensure formation of a peroxy product that will dissolve.
- an alkali tungstate such as Na 2 WO 4
- An alternate (albeit less preferred) method for forming the peroxypolytungstate solution involves digesting tungsten metal or tungsten carbide in aqueous or alcoholic peroxide solutions to form a peroxytungstic acid solution.
- the peroxypolytungstate solution is converted to a stable oxide polytungstate solution.
- One way of accomplishing the conversion is to age the peroxypolytungstate solution for an extended period of time (e.g., on the order of months).
- conversion is accomplished by drying the peroxypolytungstate solution to form a powder, dissolving the powder in an alcohol (preferably ethanol), and then refluxing the resulting solution at or near its boiling point. Drying is typically accomplished by evaporating solvent (typically water) at slightly elevated temperatures (e.g., about 40° C.). A rotary evaporator may be used for the drying step, although other drying methods such as spray drying may be used as well.
- Dissolution in alcohol is preferably effected by adding the alcoholic solvent to the dried powder, heating the resulting mixture to about 30°-60° C. (e.g., in the case where the alcohol is ethanol), and stirring the mixture until a clear solution is obtained.
- Concentrations convenient for subsequent coating formation e.g., about 10-20% by weight tungsten oxide are generally used.
- the reflux period must be sufficiently long to produce the desired oxide polytungstate solution without concurrent formation of substantial amounts of haze, precipitation, viscosity increase, or gelation, which may occur if the reflux period is too long. On the other hand, if the reflux period is too short, inadequate conversion to the oxide polytungstate may occur, resulting ultimately in tungsten oxide coatings that do not fully bleach upon de-intercalation of lithium ions.
- Typical reflux periods are on the order of about 60 minutes.
- reflux periods ranging from about 40-60 minutes have been found to produce satisfactory oxide polytungstate solutions.
- incorporation of small amounts of water may increase the reflux "window" to two hours or more. Large amounts of water, however avoided because they may result in optical defects and/or inadequate conversion, resulting ultimately in tungsten oxide coatings that do not fully bleach upon de-intercalation of lithium ions.
- the amount of water is no greater than about 20% by weight (which translates to about 15 moles of water per mole of tungsten for a peroxypolytungstate solution having 17% by weight tungsten oxide).
- the amount of water ranges from about 2 to about 8% by weight.
- the resulting oxide polytungstate solutions are stable, as defined above.
- the above-described solution prepared from AMT is stable for periods up to 50 days at room temperature, and for at least several months when refrigerated at a temperature of about 5°-10° C. Stability may be enhanced further through incorporation of additives such as 2,4-pentanedione.
- the solution may further include other additives as well.
- the solution may include inorganic additives such as TiO 2 that affect the structure and properties of the final tungsten oxide coating.
- additives which may be included are fugitive organic materials that may affect solution stability or oxide microstructure.
- the solution is preferably applied to the surface of a substrate (e.g., a glass or plastic substrate provided with a transparent conductor), dried to solid form, and then heated to remove any remaining solvent and transform the oxide polytungstate to tungsten oxide.
- a substrate e.g., a glass or plastic substrate provided with a transparent conductor
- Suitable application methods include dipping the substrate into the solution or spreading the solution onto the substrate surface. Heating is preferably conducted at temperatures ranging from about 100° C. to about 350° C. (more preferably from about 150° C. to about 250° C.) for a period of time ranging from about 1-40 minutes (more preferably from about 5-°minutes).
- This example describes the preparation of tungsten oxide coatings.
- ITO-coated glass plates (Libbey-Owens-Ford, Toledo, Ohio) were dipped into a beaker containing the stable oxide polytungstate solution and withdrawn at a rate of about 20 cm per minutes. The coated samples were then air-dried, after which they were heat-treated at about 225° C. for about 20 minutes in a box furnace to form an electrochromic tungsten oxide coating. Based upon the weight gain of a sample having a known surface area, the average coating thickness was calculated to be approximately 3000 angstroms, assuming a density of about 5.0 g/cm 3 for the amorphous tungsten oxide coating.
- the samples were tested using an electrochemical test apparatus consisting of a scanning potentiostat (Model 100B, available from Bioanalytical Systems, West Lafayette, Ind. or Model 362,available from EG&G PARC, Princeton, N.J.), a three electrode cell containing the test electrode, a Ag/AgCl 2 reference electrode, and a Pt auxiliary electrode, and a test solution of 0.1N CF 3 SO 3 Li (available as FC-122 from 3M, St. Paul, Minn.) or lithium trifluoromethanesulfonylimide (available as HG-115 from 3M, St. Paul, Minn.) in acetonitrile. Charging and discharging were done at -1.0 and +1.0 volts, respectively.
- a scanning potentiostat Model 100B, available from Bioanalytical Systems, West Lafayette, Ind. or Model 362,available from EG&G PARC, Princeton, N.J.
- FC-122 available as FC-122 from 3M, St. Paul
- Charge uptake and discharge were measured using a coulombmeter, and optical properties were measured using an integrated optical densitometer featuring a quartz halogen lamp Type 2604-A equipped with a blue filter (Photographic Type 80-A) as a light source that corrects temperature to approximate day light.
- the detector was a crystalline silicon photodiode.
- uncharged samples exhibited an average integrated transmission of about 79-81%.
- Highly charged samples e.g., samples charged at -1.0 V until the charging current fell to about 1 mA per 20 cm 3 ) had charges of 20-30 mC per cm 2 and exhibited an average integrated transmission of about 14-20%. After bleaching at +1.0 V, the average integrated was again about 79-81%.
- Tungsten oxide-coated samples were prepared according to the procedure of Example 1, but with the following changes.
- About 24.2 g of sodium tungstate (Na 2 WO 4 +2H 2 O) was used instead of ammonium metatungstate and combined with 150 g of distilled, de-ionized water.
- a larger ion exchange column provided with 450 cm 3 of ion exchange resin was used for the acidification step.
- the acidified solution was collected directly into a beaker containing about 10 g of 30% hydrogen peroxide solution.
- the coated glass samples were heated at 175° C. for 15 minutes.
- the average initial integrated transmission, charged transmission, and discharged transmission values were about 80-81%, 18-28%, and 79-81 %, respectively.
- a peroxytungstic acid solution was prepared by adding 8 g of tungsten metal powder (Alfa Chemicals, -22 mesh, 99.999%) to a mixture of about 50 g of distilled, de-ionized water and 50 g of 30% aqueous hydrogen peroxide. The powder was added slowly with stirring over a period of about 1 hour, after which the reaction was continued for about 24 hours and filtered to yield a clear solution containing the peroxytungstic acid. A platinum mesh was immersed in the solution for several minutes to decompose any unreacted hydrogen peroxide.
- Example 2 Tungsten oxide-coated glass samples were prepared and tested according to the procedure described in Example 2. The initial, charged, and discharged integrated transmission values were 81%, 21%, and 79%, respectively.
Abstract
Description
Claims (31)
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US08/639,020 US5772978A (en) | 1996-04-24 | 1996-04-24 | Process for producing tungsten oxide |
EP97916091A EP0895508B1 (en) | 1996-04-24 | 1997-03-19 | Tungsten oxide solution and process for producing the same |
CA002250429A CA2250429C (en) | 1996-04-24 | 1997-03-19 | Process for producing tungsten oxide |
JP53805797A JP4113938B2 (en) | 1996-04-24 | 1997-03-19 | Method for producing tungsten oxide |
PCT/US1997/004408 WO1997039980A1 (en) | 1996-04-24 | 1997-03-19 | Process for producing tungsten oxide |
DE69725127T DE69725127T2 (en) | 1996-04-24 | 1997-03-19 | Tungsten oxide solution and process for its manufacture |
US09/012,540 US5911965A (en) | 1996-04-24 | 1998-01-23 | Process for producing tungsten oxide |
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US08/639,020 US5772978A (en) | 1996-04-24 | 1996-04-24 | Process for producing tungsten oxide |
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EP (1) | EP0895508B1 (en) |
JP (1) | JP4113938B2 (en) |
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US5911965A (en) * | 1996-04-24 | 1999-06-15 | Minnesota Mining And Manufacturing Company | Process for producing tungsten oxide |
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US11139433B2 (en) * | 2016-01-12 | 2021-10-05 | Centre National De La Recherche Scientifique | Tungstate ion solution and hybrid photovoltaic device |
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WO1997039980A1 (en) | 1997-10-30 |
EP0895508B1 (en) | 2003-09-24 |
JP2000510085A (en) | 2000-08-08 |
DE69725127D1 (en) | 2003-10-30 |
US5911965A (en) | 1999-06-15 |
JP4113938B2 (en) | 2008-07-09 |
DE69725127T2 (en) | 2004-07-08 |
EP0895508A1 (en) | 1999-02-10 |
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